A wireless position determining technology is a technology for determining a position of a terminal in a satellite navigation system such as a global positioning system (GPS), or a wireless communication system such as code division multiple access (CDMA) wireless local area network (WLAN), ultra wideband (UWB), Bluetooth, etc. Currently, the utilization of the wireless position determining technology is being expanded with the increase in demand for position information.
The GPS plays a role of an infrastructure with very high precision, but has a problem in that it does not cover every location. In detail, a first problem of the GPS is in that a GPS signal cannot be received in an area that is not visible from a satellite with regard to a line-of-sight (hereinafter referred to as “LOS”), and in particular, in most structure interiors. For example, in the case of a mobile phone, a mobile phone in which a GPS receiver is mounted uses GPS position determination with only a probability of about 25%. In order to overcome the problem, a method for retransmitting the GPS signal from the ground can be considered. In this case, since a distance from a receiving node to a terrestrial station and a distance from the receiving node to a satellite station are different from each other and the terrestrial station should be built inexpensively, a signal interference problem, a near-far problem, a synchronization problem, etc., occur. A second problem of the GPS is in that only the receiving node in which the GPS receiver is mounted can receive the GPS signal.
Therefore, wireless position determining technologies, which have degraded performance as compared to the position determining technology using the GPS but can be used in an environment where the GPS cannot be used, have been researched. Even in the environment in which the GPS cannot be used, transmitting ends and receiving ends that previously know the position are present.
In case of downlink wireless position determination, a node that wishes to know the position receives a signal from transmitting stations and uses information on the signal so that it directly performs the position determination or provides the information to a network to perform the position determination.
As a wireless position determining method other than the downlink wireless position determining method, there are an angle of arrival (AOA) method, a time of arrival (TOA) method, a time difference of arrival (TDOA) method, a received signal strength indicator (RSSI) method, etc.
The AOA method, which uses an angle of a received signal, has a problem in significantly degrading precision in the case where there is no LOS.
The RSSI method, which uses received signal strength, has a problem in causing a large error due to radio wave shadowing and fast fading.
The TOA and TDOA methods, which use a time of received signal, that is, a delay value, are relatively frequently used as compared to the AOA or RSSI method. However, the transmission signal used in the TOA and TDOA methods is spread on a time axis through a radio channel. At this time, each of the spread time delay taps has a relatively random size. For this reason, a delay tap having a dominant size can be changed every moment, such that the TOA and TDOA methods have a problem as to which time position is selected as the delay value and in degrading precision.
The above information disclosed in this. Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.